Abstract
The treatment of end-of-life vehicles generates large amounts of automobile shredder residue (ASR), a potential source of recycled metals. Reliable measurement methods are required to determine the composition of ASR and evaluate the resource potential. We reported on research undertaken to investigate bias and variability in the process of measuring trace metals in ASR. Two primary samples of shredder light fraction (SLF) underwent extensive physical sample preparation and chemical analysis. The samples were spiked to control random variations and systematic effects during physical sample preparation. Chemical analysis was conducted using wavelength-dispersive X-ray fluorescence spectrometry (WD-XRF), a fully validated wet-chemical analysis, and a wet-chemical analysis representing an “in-house” lab procedure. Physical sample preparation introduced deviations up to a factor of 2, likely due to preferential losses and heterogeneity. Deviations for WD-XRF measurements of elements were in the range +100%/−50%. In-house chemical analysis produced results that were in good agreement with validated results for Al, Fe and Sn, but led to biased results or high variability for Cd, Dy, La, Nd, Pb, Pd, Pt and Sb. To improve the chemical analysis of trace metals in SLF, we recommended reducing particle size to less than 0.1 mm before chemical analysis and using a larger number of repeated digestions.
Highlights
Each year, more than 6 million end-of-life vehicles (ELVs) are treated in the European Union [1].After being depolluted and dismantled, the ELV hulks are treated in shredders to mechanically liberate and separate base metals, mainly steel and aluminum, from other materials
We report on work undertaken to address these three points for trace metals in automobile shredder residue (ASR), shredder light fraction (SLF), which constitutes the majority of ASR
We focused on the sample preparation and chemical analysis phases while acknowledging that sampling provides a very important contribution to uncertainties
Summary
More than 6 million end-of-life vehicles (ELVs) are treated in the European Union [1]. To complete the measurement process, the final test sample (e.g., 0.1 g of material) goes through a chemical analysis procedure, which is usually conducted in two steps: chemical or physical treatment followed by detection of the analyte [11]. Systematic deviations may have various causes, including but not limited to incomplete dissolution of the matrix material, chemical reactions between the analyte and other constituents followed by precipitation or evaporation, and overlapping spectra between the analyte and other constituents Such effects are more likely to influence the measurement when the sample contains a large variety of materials and substances, as is the case for ASR. The overall objectives and approach were the same as in our recent study on the chemical analysis of printed circuit boards [35]
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